1. Field of the Invention
The present invention relates to dimming control of a typical automotive module utilizing a vacuum fluorescent display. More particularly, the present invention relates to dimming of a module capable of utilizing three different types of dimming control methods.
2. Background Art
Nighttime dimming control of a typical automotive module (e.g., radio, instrument cluster, etc.) utilizing a vacuum fluorescent display (VFD) has been accomplished in a module in one of three methods. The first type of dimming control is that of analog DC voltage. A DC control voltage applied to a radio dimming input VFD driver IC will generate a VFD driving voltage proportional to the input voltage.
A second type of dimming control is pulse width modulation (PWM). A PWM dimming module varies the pulse width and hence the duty cycle of a waveform applied to a radio dimming input. The voltage input to the input control port of a VFD driver IC will generate the VFD driving voltage based on a prearranged VFD duty cycle ratio.
A third type of dimming control is accomplished using predetermined formatted multiplex bus messages. A dimming command is sent to a module over a multiplex bus. In response to the bus message, a module dims the VFD depending on the predetermined intensity for a given message.
Analog DC voltage dimming and PWM dimming have been accomplished in the same module and are known in the art. However, no module has been designed to be simultaneously compatible with all three dimming methods.